A burner for use in furnaces such as in steam cracking. The burner includes a primary air chamber for providing at least a portion of the combustion air, a burner tube having an upstream end and a downstream end, a fuel orifice located adjacent the upstream end of the burner tube, for introducing gaseous fuel into the burner tube, a burner tip having an outer diameter mounted on the downstream end of the burner tube adjacent a first opening in the furnace, so that combustion of the gaseous fuel takes place downstream of the burner tip producing a gaseous fuel flame, at least one non-gaseous fuel gun, the at least one non-gaseous fuel gun having at least one fuel discharge orifice, the at least one non-gaseous fuel gun being radially positioned beyond the outer diameter of the burner tip, wherein the at least one non-gaseous discharge orifice of the at least one non-gaseous fuel gun is positioned so that the non-gaseous fuel is injected into the gaseous fuel flame, whereby a portion of the non-gaseous fuel flame vaporizes prior to combustion and stabilizes the non-gaseous fuel flame.